A persistent problem with boats and ships has long been marine fouling. Various attempts have been made to alleviate such fouling from such creatures as barnacles.
An attempt to that end by ultrasonic vibration of ship hulls, with oscillators coupled inside the hulls, was disclosed in a Russian publication: "Transactions. Technical Operations of the Maritime Fleet. Thermochemical Studies. Control of Corrosion and Fouling. Central Scientific Research Institute of the Maritime Fleet No. 160, 1972."
Piezofilm, so called polymer sheet producing mechanical deformation in both lengthwise and thickness (and widthwise) directions when subjected to voltages therethrough, is disclosed in Murayama et al. U.S. Pat. No. 3,792,204, "Acoustic Transducer Using a Piezoelectric Polyvinylidene Fluoride Resin Film as the Oscillator", granted Feb. 12, 1974, and in a brochure "Kureha KF Piezofilm", published by Kureha Chemical Industry Co., Ltd.
Other attempts at antifouling devices are disclosed in Taylor U.S. Pat. No. 2,435,986, "Antifouling Device", granted Feb. 17, 1948.